Low profile delivery system for stent and graft deployment and method for deployment

ABSTRACT

A delivery system for endoluminal deployment of a stent inside of a biocompatible graft cover minimizes obstruction of endoluminal fluid flow during deployment. The delivery system comprises a stent sheath, a compressed stent underlying the stent sheath, and a graft overlying the stent sheath and releasably retained in a compressed state surrounding the sheath. The graft distal end is attached to the stent at or proximal the stent distal end, and the graft outer surface is exposed to the interior space of the lumen during deployment. The proximal end of the graft may be attached to the stent sheath by a releasable attachment adapted for release during deployment of the stent, or may be otherwise constrained, such as by heat deformation, to remain adjacent the outer circumference of the stent prior to deployment. The releasable attachment may be a suture that is severed by a pusher having a cutter therein. The delivery system may further include an inner core underlying the stent and connected to a tip sheath that overlies the stent distal end. One method of deploying the stent and overlying graft comprises advancing the tip sheath to allow the stent distal end to expand, retracting the stent sheath to cause the suture to be severed by the pusher cutter therefore allowing endoluminal fluid to flow between the graft and the sheath, and then completing deployment of the stent to urge the graft against the lumen wall.

This application is a continuation of U.S. patent application Ser. No.09/923,898, filed Aug. 7, 2001 (issued as U.S. Pat. No. 6,416,536 onJul. 9, 2002), which is a divisional of U.S. patent application Ser. No.09/337,120, filed Jun. 21, 1999 (issued as U.S. Pat. 6,398,802 on Jun.4, 2002).

TECHNICAL FIELD

The present invention relates generally to endoluminal grafts or“stents” and, more specifically, to a stent delivery system or“introducer” for deploying a stent inside of a prosthetic graft withoutinterrupting fluid flow during deployment and a method for suchdeployment.

BACKGROUND OF THE INVENTION

A stent is an elongated device used to support an intraluminal wall. Inthe case of a vascular stenosis, a stent provides an unobstructedconduit for blood in the area of the stenosis. An intraluminalprosthesis may comprise a stent that carries a prosthetic layer of graftmaterial. Such a prosthesis may be used, for example, to treat avascular aneurysm by removing the pressure on a weakened part of anartery so as to reduce the risk of rupture. Typically, an intraluminalstent or prosthesis is implanted in a blood vessel at the site of astenosis or aneurysm endoluminally, i.e. by so-called “minimallyinvasive techniques” in which the stent, restrained in a radiallycompressed configuration by a sheath or catheter, is delivered by astent deployment system or “introducer” to the site where it isrequired. The introducer may enter the body through the patient's skin,or by a “cut down” technique in which the entry blood vessel is exposedby minor surgical means. When the introducer has been threaded into thebody lumen to the stent deployment location, the introducer ismanipulated to cause the stent to be released from the surroundingsheath or catheter in which it is restrained (or alternatively thesurrounding sheath or catheter is retracted from the stent), whereuponthe stent expands to a predetermined diameter at the deploymentlocation, and the introducer is withdrawn. Stents are typically expandedby spring elasticity, balloon expansion, or by the self-expansion of athermally or stress-induced return of a memory material to apre-conditioned expanded configuration.

Referring now to a stent deployment system of the prior art in FIG. 1,there is shown an endoluminal prosthesis 10 comprising a wire stent 12affixed along its length to an outer graft cover 14, the graft and stentcompressed inside outer sheath 16 (shown in cross-section). During thedeployment process of endoluminal prosthesis 10 in a body lumen 20, suchas a blood vessel, outer sheath 16 is retracted, and stent 12 expandsagainst the walls 19 of the lumen 20 (shown in cross-section). Duringthe expansion process, the partially-deployed, covered section 22 atdistal end 23 and middle section 25 of integral stent/graft prosthesis10 can block the flow of blood along arrow A temporarily until proximalend 24 is released from the sheath. As used herein, “proximal” isdefined as meaning “closer to the end of the introducer remainingoutside the body”, whereas “distal” is defined as meaning “farther fromthe end of the introducer remaining outside the body”. Duringdeployment, the pressure of obstructed blood flow at covered section 22may cause the prosthesis to migrate away from its intended location orbecome longitudinally compressed. If for some reason the deploymentprocedure becomes protracted, the blood flow blocked by covered section22 may impart serious stress upon the patient. Thus, it is desirable toprovide for unobstructed blood flow throughout the stent deploymentprocess.

A construction known to the inventor prior to this invention comprises adevice shown in FIG. 2 comprising stent 12′ and outer graft cover 14′joined by a connection 30 to stent 12′ proximal the distal end 23thereof. Prior to deployment, stent 12′ and graft liner 14′ arerestrained in a compressed configuration by an outer sheath 16′surrounding both the stent and the liner, and by an inner sheath 38disposed between stent 12′ and liner 14′ proximally of connection 30.Deployment of this prosthesis is effected by first retracting outersheath 16′, allowing distal portion of stent 12′ and then cover 14′ tofully expand independently. Stent 12′ is subsequently fully expandedproximal of the connection point by retracting inner sheath 38. Duringdeployment of this device, blood flow can continue as indicated byarrows B.

The introducer construction having two sheaths as described abovenecessarily requires an introducer of somewhat larger diameter andlesser flexibility than most such introducers known in the art havingonly a single sheath.

SUMMARY OF THE INVENTION

The present invention provides a flexible, single-sheath, low-profiledelivery system for deployment of a stent inside of a biocompatiblegraft cover in a distal deployment location in a body lumen from aproximal access location outside the body lumen. The delivery systemcomprises a stent sheath having a distal end located upstream relativeto the fluid flow; a compressed stent underlying the stent sheath, thestent having a proximal end housed within the stent sheath and a distalend; and a compressed biocompatible graft cover overlying the stentsheath along the length of the stent and releasably retained in acompressed state surrounding the sheath. The graft has a distal endattached to the stent at or proximal the stent distal end and an outersurface exposed to the interior space of the lumen during deployment.The stent distal end may be spaced distally from the stent sheath distalend and graft attachment, in which case the delivery system may furthercomprise a tip sheath overlying the stent distal end and an inner core,optionally having a guidewire lumen therein, attached to the tip andextending axially through the stent. A pusher underlies the stent sheathproximal the stent. The pusher distal end may be rounded. The inner coreand attached tip sheath may be attached distally to the pusher, or thepusher may have an inner lumen extending axially therethrough, whereinthe inner core extends axially through the pusher inner lumen.

The stent delivery system further may comprise a temporary, protectivewrapper over the biocompatible graft, the wrapper adapted to be removedprior to insertion of the delivery system into the body lumen. Thecompressed biocompatible graft may further comprise a proximal endattached to the stent sheath by a releasable attachment, such as asuture, adapted to be released during deployment of the stent. Thesuture may be adapted for release by being secured with a slip-knotadapted to be untied during stent deployment, by the delivery systemfurther comprising a balloon adapted for breaking the suture uponinflation of the balloon, or by the pusher further comprising a cutter,such as a sharpened hypotube, adapted for severing the suture uponmovement of the pusher relative to the stent sheath.

Specifically, the stent sheath may have a suture connection point, suchas a pair of tie-holes, in its circumference and radially-opposite firstand second through-holes, with the pusher having a window in its distalend aligned with the stent sheath through-holes and having the cutterproximally located therein. In such a configuration, the opposite endsof the suture are attached to the suture connection point, and anintermediate section of the suture is threaded through the graft in oneor more locations, through the sheath through-holes, and through thepusher window.

The invention further comprises a method for endoluminally deploying astent and overlying biocompatible graft cover without obstructing fluidflow during deployment, as follows. First, the stent and graft arecompressed and loaded into a single-sheath-profile stent delivery systemas described herein. Then, the stent delivery system is inserted into abody lumen and navigated through the lumen until the stent is at adesired deployment location. Next, the stent sheath is proximallydisplaced relative to the stent distal end, the stent distal end becomesexpanded, and endoluminal fluid flows between the stent sheath and thegraft so that the graft becomes radially distanced from the stentsheath. Finally, deployment of the stent is completed so that it biasesthe graft against the body lumen.

Where the stent delivery system further comprises a tip having a tipsheath overlying the distal end of the stent and attached to an innercore extending axially through the stent, the method further comprises,prior to proximally displacing the stent sheath relative to the stent,first releasing the stent distal end from the tip sheath by displacingthe inner core distally relative to the stent sheath. Where the pusheris attached to the inner core, displacing the inner core distallyrelative to the stent sheath comprises a single, continuous, proximalretraction of the stent sheath that also displaces the pusher distallyrelative to the stent sheath to deploy the stent. Where the pusher hasan inner lumen axially therethrough through which the inner core ismounted, displacing the inner core distally relative to the stent sheathcomprises first advancing the inner core distally relative to the stentsheath to release the stent distal end from the tip sheath, and thenretracting the stent sheath to deploy the stent. Where the proximal endof the graft is attached to the sheath with a releasable attachment suchas a suture, the attachment is released prior to endoluminal fluidflowing between the graft and the sheath. Where the releasableattachment is a suture, the step of moving the stent sheath relative tothe pusher may cut the suture.

The method may further comprise suturing the graft to the stent sheathby the steps of anchoring a first end of the suture through thetie-holes, extending the suture along the stent sheath; piercing thegraft one or more times with the suture; extending the suture along thestent sheath; entering the stent sheath radially through one of thethrough-holes, extending the suture through the pusher window, andexiting the stent sheath through the opposite through-hole; extendingthe suture along the stent sheath; piercing the graft one or more timeswith the suture; extending the suture semi-circumferentially around thesheath; and anchoring a second end of the suture to the tie-holes.

After deployment, the stent delivery system may be prepared forwithdrawal by advancing the pusher into the tip sheath and advancing thestent sheath until the distal end of the stent sheath is adjacent theproximal end of the tip sheath, and then withdrawn. Prior to insertioninto the body, the stent sheath may be locked to the pusher and theinner core biased under slight tension and locked to the pusher. In suchcase, deployment further comprises unlocking the inner core from thepusher prior to moving the inner core distally and unlocking the stentsheath from the pusher prior to retracting the stent sheath.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary, but are notrestrictive, of the invention.

BRIEF DESCRIPTION OF DRAWING

The invention is best understood from the following detailed descriptionwhen read in connection with the accompanying drawing. It is emphasizedthat, according to common practice, the various features of the drawingare not to scale. On the contrary, the dimensions of the variousfeatures are arbitrarily expanded or reduced for clarity. Included inthe drawing are the following figures:

FIG. 1 is a longitudinal section schematic illustration of an exemplaryendoluminal prosthesis delivery system of the prior art.

FIG. 2 is a longitudinal section schematic illustration of an exemplarystent delivery system known to the inventor prior to this invention.

FIGS. 3A-3C are longitudinal section schematic illustrations of anassembled exemplary stent delivery system of the present invention, andenlarged portions thereof, respectively.

FIGS. 4A and 4B are schematic illustrations of a crochet weave securinga graft to the stent sheath, shown in partial longitudinal section, andof the loops of an exemplary crochet configuration, respectively.

FIG. 5 is a longitudinal section schematic illustration of a graftsecured to the stent sheath with an adhesive.

FIGS. 6A-6C are schematic illustrations of an exemplary graft and anexemplary stent sheath to which the graft is adapted to be releasablysecured, a longitudinal section of such graft and stent sheath showingthe graft in a secured configuration, and a longitudinal section of thegraft and stent sheath showing the graft in a released configuration.

FIGS. 7A-7C are longitudinal section schematic illustrations of thestent delivery system of FIGS. 3A-3C during sequential deployment steps.

FIG. 7D is a partial longitudinal section schematic illustration of thedeployed stent and the stent delivery system prepared for withdrawalafter the deployment step shown in FIG. 7C.

FIG. 8 is a flowchart depicting exemplary method steps for deployment ofa stent and graft according to the present invention.

FIG. 9 is a longitudinal section schematic illustration of an alternateembodiment of an assembled exemplary stent delivery system of thepresent invention.

FIGS. 10A and 10B are a longitudinal section schematic illustration ofan exemplary introducer embodiment wherein the graft is secured via aslip knot, and a detailed illustration of the knot, respectively.

FIG. 11 is a partial longitudinal section schematic illustration of adistal portion of an exemplary stent delivery system having a crochetweave securing the distal end of the stent.

DETAILED DESCRIPTION OF THE INVENTION

The entire disclosure of U.S. patent application Ser. No. 09/923,898,filed Aug. 7, 2001 now U.S. Pat. No. 6,416,536 B1, is expresslyincorporated by reference herein.

Referring now to the drawing, wherein like reference numerals refer tolike elements throughout, FIGS. 3A-3C illustrate an exemplary introduceraccording to the present invention for endoluminal deployment of a stentinside of a biocompatible graft cover without obstructing endoluminalfluid flow during deployment. As shown in FIGS. 3A-C, exemplary stentdelivery system 40 comprises a stent sheath 42, a compressed stent 44underlying the stent sheath, a pusher 46 underlying the stent sheathproximal to the stent, an inner core 48, and a compressed biocompatiblegraft 50 overlying distal end 52 of the stent sheath. Inner core 48 isaxially mounted within inner lumen 56 of pusher 46, extends axiallythrough stent 44 and attaches to tip 58 comprising tip sheath 60overlying distal end 62 of the stent. Optional central guidewire lumen49 (not shown in FIG. 3A) runs through inner core 48 and tip 58, asshown in FIGS. 3B and 3C. Graft 50 has a distal end 64 attached to thestent by attachment 51 distally of the sheath distal end 52. Optionally,attachment 51 may be located at or somewhat proximally of the distal end52 of sheath 42 within sheath 42, so long as the part of graft 50 lyingwithin sheath 42 is easily pulled or otherwise disposed distally ofsheath 42 during deployment. Graft 50 further has a proximal end 66attached to stent sheath 42 by a releasable attachment, such as suture68, adapted to be released during deployment of the stent. As shown inFIGS. 3A-C, pusher 46 has a rounded distal end 47.

Although stent delivery system 40 has both a tip sheath 60 and a stentsheath 42, the two sheaths abut one another axially and have the sameouter diameter. Thus, the two sheaths together in series form asingle-sheath-profile stent delivery system, meaning that the profile ofthe stent delivery system is no greater than that provided by a singleouter sheath plus graft material. Other embodiments having no tip sheath60, are discussed below.

The stent may be self-expanding, comprising, for example, a shape-memorymaterial such as nitinol, or may be any type of elastically or thermallyexpandable stent known in the art. The biocompatible graft material maybe polyester, polyurethane, polyethylene, polytetrafluoroethylene(PTFE), or any material known in the art. The stent deployment system ofthe present invention may be used for deployment of stents and graftswithin blood vessels or in other body lumens, such as in the trachea. Asused herein, the term “stent delivery system” shall encompass both acompleted assembly which is capable of deploying a stent or asub-assembly which is capable of deploying a stent when combined withother components

To effect release of the suture 68 during deployment, pusher 46 furthercomprises at distal end 47 a window 76 in which is proximally mountedcutter 70, such as a sharpened hypotube, adapted for severing the sutureupon movement of the pusher relative to stent sheath 42. Stent sheath 42has a connection point, such as a pair of tie-holes 72, as shown in FIG.3C, and a pair of radially opposite through-holes 74. Window 76 isradially aligned with stent sheath through-holes 74 prior to and duringintroduction of stent delivery system 40 into the body. As shown in FIG.3C, suture 68 is anchored at one end through tie-holes 72 and extendsdistally along stent sheath 42 from the tie-holes along arrow “C”,pierces graft 50 one or more times along arrow “D”, returns proximallyalong the stent sheath along arrow “E”, turns radially in the directionof arrow “F” and enters the stent sheath through one through-hole 74,extends through pusher window 76 and exits the stent sheath through theother through-hole 74, extends distally along the stent sheath alongarrow “G”, pierces the graft one or more times along arrow “H”, extendssemi-circumferentially around the stent sheath along arrow “I” (shown indashed lines) and anchors to the tie holes or to the other end of thesuture. Suture 68 may be attached by a method that follows the orderdescribed above, starting along arrow C in alphabetical order througharrow I, or in reverse order, starting in the direction opposite arrowI, and following reverse alphabetical order in the opposite direction ofeach arrow named above. This suture configuration reduces frictionbetween the suture and graft during deployment because the suture is cutinto two short lengths to be pulled through the graft rather than onelong length of suture.

Other suture configurations may also be used to anchor graft 50 to stentsheath 42 and to cut the suture upon deployment. Instead of the suturebeing tied through a pair of tie holes 72, the suture connection pointto stent sheath 42 may comprise any type of connection known in the art.Such connection may comprise, for example without limitation thereto, asingle hole in the stent sheath and a stopper knot tied in the end ofthe suture to prevent pulling the end through the hole, an adhesive orheat-fused bond, or a crimped metal or rubber band.

Different releasable attachment devices other than sutures may also beused. In an alternative embodiment, referring now to FIGS. 4A and 4B, acrochet weave 80 may be disposed over proximal end 66 of graft 50 tosecure it to stent sheath 42. As shown in detail in FIG. 4B, crochetweave 80 comprises a continuous filament 82 wound into n successiveloops 84 i-n helically wrapped around the graft in alternatingorientations (loop 84 i counterclockwise, loop 84 ii clockwise, loop 84iii counterclockwise, and so on, viewed from loop 84 i lookingproximally), the stem 86 of each loop protruding through the hole 88made by the preceding loop. Distal end 90 of filament 82 is typicallyreleasably secured to provide resistance to unwinding of crochet weave80, such as by being pulled through a slot 91 in tip sheath 60 andpinched therein. Proximal end 92 of the filament is tucked withinthrough-hole 74 in stent sheath 42, as shown in FIG. 4A, and trailedwithin the stent sheath to the outside of the body. Filament 82 may thenbe pulled like a drawstring to untie crochet weave 80 loop by loop andto pull distal end 90 out of slot 91. Although FIG. 4A shows sheath 42and graft 50 in longitudinal section to illustrate through-hole 74 andtrailing proximal end 92, crochet weave 80 is illustrated in itsentirety without hidden portions, to show location. FIG. 4B showscrochet weave 80 as visible from one side of graft 50.

In another alternative embodiment, referring now to FIG. 5, graft 50 maybe tacked to stent sheath 42 with a bead of biocompatible adhesive 100that softens or dissolves after a certain amount of time of exposure toblood (or other intraluminal fluid in the lumen in which the stent is tobe deployed), thus allowing the graft to be pulled away from stentsheath 42 upon deployment.

In yet another alternative embodiment, referring now to FIGS. 6A-6C,graft 650 may have a tab 651 at the proximal end 66 thereof, the tabadapted to be inserted in slot 674 in stent sheath 642. Tab 651 is thenreleasably secured by being pinched between stent sheath 642 and pusher646, as shown in FIG. 6B. Pusher 646 has an indent 676 adjacent thepusher distal end 647 such that when sheath 642 is retracted proximallyor pusher 646 is advanced distally, indent 676 aligns with slot 674 instent sheath 642 such that tab 651 is released and graft 650 is free todeploy, as shown in FIG. 6C. As shown in FIGS. 6B and 6C, tab 651 may becompletely inserted within slot 674 and its end pinched between pusher676 and the inside wall of stent sheath 642 as shown with respect to topslot 674, or as shown with respect to bottom through-hole 674′, portion651′ of graft 650 may be doubled over on itself with the end outside theslot. Portion 651′ inserted within slot 674′ may be a discrete tab, orif the materials of construction of graft 650 so allow, portion 651′ mayrather be a portion of graft 650 that is merely pushed into through-hole674, doubled over on itself, and pinched.

Introducer 40 is used to carry out a method for endoluminally deployinga stent and overlying graft without blocking endoluminal fluid flowduring deployment, as shown in FIGS. 7A-D. First, stent 44 and overlyinggraft 50 are compressed and loaded into stent delivery system 40 havingthe components previously described herein and assembled as shown inFIG. 3A. Next, the stent delivery system is navigated to a desireddeployment location over a guidewire (not shown) or by other means knownin the art. Then, at the deployment location, stent distal end 62 isreleased by moving inner core 48 distally relative to stent sheath 42along arrow Z, as shown in FIG. 7A. Then, stent sheath 42 is retractedproximally relative to stent 44 along arrow Y, thus pulling suture 68 inwindow 76 across cutter 70 of pusher 46 and severing the suture as shownin FIG. 7B. With suture 68 cut, graft 50 expands so that blood or otherendoluminal fluid flows along arrows B through stent 44 and betweenstent sheath 42 and the graft, as is shown in FIG. 7C. Suture 68 isretained on stent sheath 42 in two pieces, each piece tied at one endthrough tie-holes 72 in the stent sheath and carried by the motion ofthe stent sheath and the endoluminal fluid flow in the direction ofarrow B. Stent sheath 42 is retracted along arrow Y until stent 44 iscompletely deployed in a configuration biasing graft 50 against thewalls 19 of the body lumen 20, as shown in FIG. 7D.

Stent delivery system 40 may then be prepared for withdrawal from thebody by advancing pusher 46 inside tip sheath 60 and advancing stentsheath 42 until it is adjacent to the tip sheath as also shown in FIG.7D. Rounded distal end 47 of pusher 46 is advantageous for guiding thepusher into tip sheath 60, which is especially useful when stentdelivery system 40 is used in an area of curved anatomy. With the stentdelivery system 40 in a closed configuration as shown in FIG. 7D, tipsheath 60 is less likely to snag on stent 44 or on walls 19 of lumen 20during withdrawal, than if left in an open configuration with a gapbetween stent sheath 42 and the tip sheath, such as is shown in FIG. 7C.

Prior to deployment, stent sheath 42 may be locked to pusher 46 andinner core 48 may also be locked to the pusher. The locking of thesecomponents together is typically accomplished at the handles located atthe proximal end of the delivery system (not shown) and that remainoutside the body during the deployment procedure. Inner core 48 may alsobe biased under slight tension prior to locking and introduction ofstent delivery system 40 into the body lumen so that tip sheath 60 doesnot become displaced relative to stent sheath 42 in curved anatomy.Thus, when stent delivery system 40 is introduced into the body in alocked configuration, the step of advancing inner core 48 relative tostent sheath 42 first comprises unlocking the inner core from pusher 46prior to moving the inner core. Similarly, the step of retracting stentsheath 42 further comprises unlocking the stent sheath from pusher 46prior to moving the sheath. Thus, one exemplary method for deployment ofa stent and graft according to the present invention may include all thesteps as depicted in the self-explanatory flowchart of FIG. 8.

Inner core 48 attached to tip 58 (and attached to tip sheath 60, wherepresent) may be mounted axially through inner lumen 56 of pusher 46 asshown in FIGS. 3A-C and 7A-D, or, referring now to FIG. 9, inner core148 may instead be mounted to distal end of pusher 146. In such aconfiguration when tip sheath 60 is also present, sheath 42 is retractedin a single motion in the direction of arrow Y to simultaneously pulldistal end 62 of stent 44 from out of tip sheath 60, allowing it toexpand, while also severing suture 168 against cutter 170 within pusher146. As retraction of sheath 42 continues in the direction of arrow Yafter stent distal end 62 is expanded, the proximal end 66 of stent 44contacts distal end 47 of pusher 146, which then pushes the stent outfrom within stent sheath 42.

Also illustrated in FIG. 9 is a temporary protective wrapper 150 overgraft 50. The wrapper may be adapted to be split or otherwise peeled ortorn away prior to inserting the delivery system within the body lumen.Such a temporary wrapper protects the graft and keeps it compressedagainst the sheath until just prior to deployment. Such a wrapper may beheat-set in place during a heat setting step that also may heat-set thegraft into a low profile. This wrapper may be particularly useful in anembodiment of this invention wherein the proximal end of the graft isnot attached to the sheath at all (not shown), but instead remains inits heat-set position wrapped about stent sheath 42 until stent 44starts to expand. The heat-set configuration is undone as stent 44expands and blood flows between graft 50 and stent sheath 42.

Further illustrated in FIG. 9 is an embodiment wherein suture 168 issecured to graft 50 rather than being secured through tie-holes in stentsheath 42. In this configuration, when suture 168 is broken, it remainsconnected to graft 50 rather than to sheath 42. Suture 168 preferablycomprises a resorbable suture material to reduce risk of embolism fromthe trailing suture segments.

In yet another embodiment, the suture used for attaching the graft tothe sheath may be a slip knot 200, such as shown in FIGS. 10A and 10B,that may be untied to release the suture. Exemplary slip knot 200, asshown in more detail in FIG. 10B, may comprise a first suture 202 and asecond suture 204 that each hold down graft 50 and are secured to stentsheath 42 at a connection point, such as at tie holes 72, and a thirdsuture 206 that has a slipped end 208. Slipped end may be attached topusher 246 (as shown in FIG. 10A) or to the inner core (not shown) sothat relative movement of the stent sheath relative to the pusher orinner core unties the knot, or the slipped end may be trailed as adrawstring outside the body lumen. First suture 202, second suture 204,and third suture 206 each also have free ends 203, 205, and 207,respectively, that are tied together in slip knot 200. Knot 200 asillustrated in FIG. 10B is a modified sheet bend, shown prior totightening, for clarity. Other slip knot configurations known in the artmay also be chosen, based on suture properties and manufacturingconsiderations.

To provide a slip knot embodiment such as shown in FIG. 10A, slip knot200 may be first created at free end 203 of first suture 202, free end205 of second suture 204, and free end 207 of third suture 206 havingslipped end 208 attached to pusher 246. Then the ends of sutures 202 and204 opposite free ends 203 and 205, respectively, are threaded insidesheath 42 and out through through-holes 74, and pusher 246 is threadedinside sheath 42 into its position for deployment into the body lumen.Sutures 202 and 204 may then be secured to graft 50 and tie-holes 72 asshown in FIG. 10A.

Attachment means other than sutures may also be used for securing theproximal end of the graft to the sheath, or as mentioned above, thesheath may be left unattached at the proximal end, constrained about thesheath only by the effects of a heat-set step. Alternatively, the fluiddynamics of opposing blood flow may be sufficient to retain the proximalend circumference of the graft and preclude flow obstruction by thegraft both prior to and during deployment.

Distal end 62 of stent 44 may extend distally of distal end 64 of graft50 as shown in the embodiment illustrated in FIGS. 3A-C and 7A-D, or thegraft distal end may be attached directly to the stent distal end. Wherethe stent and graft distal ends are attached, tip sheath 60 isunnecessary, but tip 58 may still be present. Where stent distal end 62does extend distally of graft distal end 64, the stent distal end may besecured to core 48 by means other than tip sheath 60, as shown in FIG.3B. For instance, as shown in FIG. 11, crochet weave 80′, having adistal end 90 pinched within slot 91 in catheter tip 58 and a proximalend 92 threaded into through-hole 74 in stent sheath 42 and trailedproximally outside the body lumen to be pulled like a drawstring, can beused in accordance with the general crochet weave configurationdescribed herein earlier with respect to FIG. 4B.

Although illustrated and described herein with reference to certainspecific embodiments, the present invention is nevertheless not intendedto be limited to the details shown. Rather, various modifications may bemade in the details within the scope and range of equivalents of theclaims and without departing from the spirit of the invention.

What is claimed:
 1. A low-profile system for delivering and deploying aprosthesis comprising a graft and an underlying stent that are attachedto one another only at or near a distal end of the prosthesis, thesystem comprising: the prosthesis; a sheath positioned between the stentand the graft proximally of the distal end; and at least one non-sheathmeans for retaining the graft against the sheath at least at or near aproximal end of the prosthesis during delivery of the prosthesis and forreleasing prior to or during deployment of the prosthesis.
 2. The systemof claim 1, wherein the non-sheath means comprises a suture connectingthe graft to the sheath at or near the proximal end of the prosthesis,the suture comprising a slip-knot for untying during deployment of theprosthesis.
 3. The system of claim 2, further comprising a pusherunderlying the sheath, the pusher comprising a cutter adapted to severthe suture upon movement of the pusher relative to the sheath.
 4. Thesystem of claim 1, wherein the non-sheath means comprises a sutureconnecting the graft to the sheath at or near the proximal end of theprosthesis, the system further comprising means for severing the sutureprior to or during deployment of the prosthesis.
 5. The system of claim1, wherein the non-sheath means comprises a crochet weave around thegraft at least at or near the proximal end of the prosthesis.
 6. Thesystem of claim 1, wherein the non-sheath means comprises a bead ofbiocompatible adhesive connecting the graft to the sheath at least at ornear the proximal end of the prosthesis, the adhesive adapted to releaseafter exposure to endoluminal fluid for a predetermined amount of time.7. The system of claim 1, wherein the non-sheath means comprises a slotin the sheath, a pusher underlying the sheath, and a portion of thegraft disposed within the slot and retained between the pusher and thesheath in a first position of said sheath relative to said pusher, butreleasable in a second position of the sheath relative to the pusher. 8.The system of claim 7, wherein the pusher comprises an indented regionthat aligns with the slot in the second position.
 9. A low-profilesystem for delivering and deploying a prosthesis comprising a graft andan underlying stent that are attached to one another only at or near adistal end of the prosthesis, the system comprising: the prosthesis; asheath positioned between the stent and the graft proximally of thedistal end; and a temporary protective wrapper for retaining the graftagainst the sheath and for removing prior to introduction of theprosthesis into a body lumen.
 10. The system of claim 9, wherein thewrapper comprises a heat-set wrapper.
 11. The system of claim 10,wherein the graft comprises a low-profile, heat-set configurationradially against the sheath.
 12. A method for deploying a prosthesiscomprising a graft and an underlying stent that are attached to oneanother only at or near a distal end of the prosthesis, the methodcomprising: a) loading the prosthesis into a delivery system comprisingthe prosthesis; a sheath positioned between the stent and the graftproximally of the distal end; and at least one non-sheath means forretaining the graft against the sheath at least at or near a proximalend of the prosthesis; b) delivering the prosthesis to a desireddeployment location in the body lumen; c) deploying the prosthesis inthe desired deployment location.
 13. The method of claim 12 comprisingremoving the non-sheath means prior to step (b).
 14. The method of claim13, wherein the non-sheath means comprises a temporary protectivewrapper for retaining the graft against the sheath, and step (a)comprises a heat-setting step for setting the temporary protectivewrapper into place.
 15. The method of claim 14, wherein the heat-settingstep further comprises heat-setting the graft into a low-profileconfiguration radially against the sheath.
 16. The method of claim 15,wherein the graft maintains the low-profile configuration during step(b).
 17. The method of claim 16, wherein the graft maintains itslow-profile configuration at least until an expansion step of the stentin step (c).
 18. The method of claim 12 further comprising leaving thenon-sheath means in place during step (b), wherein step (c) comprisesmanipulating the non-sheath means to release the graft from the sheathand allowing endoluminal fluid to flow between the sheath and the graftduring deployment.
 19. The method of claim 18, wherein the non-sheathmeans comprises a suture connecting the graft to the sheath at or nearthe proximal end of the prosthesis and the suture comprises a slipknot,in which step (c) comprises untying the slipknot.
 20. The method ofclaim 18, wherein the non-sheath means comprises a suture connecting thegraft to the sheath at or near the proximal end of the prosthesis, inwhich step (c) comprises severing the suture.
 21. The method of claim20, wherein the delivery system further comprises a pusher underlyingthe sheath and comprising a cutter, in which step (c) comprises severingthe suture upon movement of the pusher relative to the sheath.
 22. Themethod of claim 18, wherein the non-sheath means comprises a crochetweave around the graft at least at or near the proximal end of theprosthesis, in which step (c) comprises undoing the crochet weave. 23.The system of claim 18, wherein the non-sheath means comprises a bead ofbiocompatible adhesive connecting the graft to the sheath at least at ornear the proximal end of the prosthesis, in which step (c) comprisesexposing the adhesive to endoluminal fluid for a predetermined amount oftime after which the adhesive releases the graft from the sheath. 24.The system of claim 18, wherein the non-sheath means comprises a slot inthe sheath, a pusher underlying the sheath, and a portion of the graftdisposed within the slot and retained between the pusher and the sheath,in which step (c) comprises moving the sheath relative to the pusher sothat an indented region in the pusher aligns with the slot and allowsthe retained portion of the graft to be released.
 25. The method ofclaim 18, wherein the delivery system further comprises a pusherunderlying the sheath, in which step (c) comprises releasing thenon-sheath means concurrently with movement of the pusher relative tothe sheath.